Rotary switch contact structure with improved washer fastening means



March 1967 P. H. KORRELL ROTARY SWITCH CONTACT STRUCTURE WITH IMPROVEWASHER FASTENING MEANS Filed May 23, 1966 Fig. 5.

Ru wa W m mH P m 0m Fig. 4 Q

a good seal to the rotor.

United States i atent Ofiiice 3,309,471 Patented Mar. 14, 1967 Iud.,assignor to Appliance Van Buren, Ind., a corpora- The present inventionrelates to electric switches.

In certain types of electrical switches, mechanical precision is of theutmost importance. Thus, in certain rotary type switches, the closing ofthe circuit should be effected within a fraction of a degree and shouldcontinue to be effected within that same fraction of the same degreethroughout the life of the switch. In the United States patent toCrimmins, 2,777,908, there is disclosed a wiper type switch which iseasly constructed within narrow mechanical tolerances and which has beenfound to maintain proper operation within narrow angular tolerances overa long and useful life. However, because of the specific design of theCrimmins switch wherein electrodes of opposite polarity are spacedrelatively closely to one another, there has been found to be room forimprovement in the insulation resistance and voltage breakdown betweencurrent carrying parts and between current carrying parts and ground ofthe Crimmins rotary switch.

One solution to this problem is disclosed in the United States patent toKorrell et al., 3,248,489. While the solution illustrated in the Korrellpatent has proved to be a substantial improvement in many respects, ithas not proved to be entirely satisfactory because the epoxy of thatpatent cannot always be depended upon to produce Consequently, importantobjects of the present invention are to provide an improved rotaryswitch wherein the electrodes are better insulated from one another thanprior art switches, to provide a rotary switch which is less subject tofailure than prior art rotary switches and to provide a rotary switchwhich has a consistently higher breakdown voltage than prior art rotaryswitches.

A further object of the present invention is to provide an improvedrotary switch.

' Still another object of the invention is to provide a rotary switchwhich is less expensive to assemble than prior art rotary switches.

A further object of the invention is to provide a rotary switch whichcan be easily assembled and disassembled without loss of parts.

Related objects and advantages will become apparent as the descriptionproceeds.

One embodiment of the present invention might involve in a switchincludin" an element formed of insulating material, a pair of electricalcontact members mounted on the element, said members each consisting ofa flattened metal piece having a pair of spaced legs, said elementhaving recesses in the face thereof which recesses receive the leg endsof the respective members, said recesses in said element and the legends therein of one member being spaced from the recesses and the legends therein of the other member, the improvement which comprises aresilient washer of insulating material having projections at theperiphery thereof which grip said element and retain said washer on saidelement, said element having indentations therein which extend betweenthe leg ends of one'member' and the leg ends of the other member, andsaid washer including raised portions formed on said washer andextending into said indentations.

The full nature of the invention will be understood from theaccompanying drawings and the following description and claims.

FIG. 1 is an exploded perspective view of certain portions of the switchof the present invention.

FIG. 2 is a perspective view of a stator plate forming a part of theswitch of FIG. 1.

FIG. 3 is a plan view of the structure of FIG. 1 showing it in assembledrelation.

. FIG. 4 is a section taken along the line 4-4 of FIG. 3 in thedirection of the arrows.

FIG. 5 is an enlarged section taken along the line 55 of FIG. 3 in thedirection of the arrows.

FIG. 6 is a perspective view of a washer forming a part of the presentinvention.

FIG. 7 is an enlarged section taken along line 77 of FIG. 3.

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiment illustrated inthe drawing and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alternations and furthermodifications in the illustrated device, and such further applicationsof the principles of the invention as illustrated therein beingcontemplated as would normally occur to one skilled in the art to whichthe invention relates.

The illustrated switch is of the rotary type and isparticularly adaptedfor assembly in a dirt or water tight housing. The particular housingshown comprises a receptacle 10 with a hermetically sealed cover plate11 and with a flange 12 for panel mounting. A shaft 15 is journalled inone side of the housing and is sealed by the packing gland 16.

Stationary contacts 17 are arranged in a circle concentric with the axisof rotation of shaft 15. The cont acts 17 may be, for example cast inthe stator plate 20 of insulating material such as the thermoplastics.In the illustrated device, the stator plate is cast integrally with theperipheral flange 21 which is externally machined to a close fit in thehousing receptacle 10. A key (not shown) or the like may be employedbetween the telescoping surfaces of the flange 21 and the housingreceptacle 10 to rotationally lock the stator in the housing receptacle.The outer ends of the contact elements 17 may be bifurcated as shown toreceive soldered connecting wires. The connecting wires may leadlater-ally through the extension 22 of the housing receptacle 10 and outof the receptacle through the aperture 25. After the cover plate 11 isin place, the space between the aperture 25 not filled by the connectingwires may be potted by suitable plotting compound injected into thespace to seal the switch.

The inner ends of the contacts 17 are machined and polished to a truecoplanar surface by chucking the stator in a lathe and turningconcentrically to the central bore 26 of the stator. The leading andtrailing edges of each contactor surface may be milled to preciselydefine the rotational position of these edges with respect to the axisof the stator. Hence, by ordinary lathe turning technique, the axis ofrotation of the rotor may be precisely located relative to the surfaceof the contacts.

The rotor of the switch comprises a disk 30 of insulating materialreceived on the reduced diameter portion 29 and retained againstrotation relative to the shaft by the straight course knurl 28. The diskbears on one side against the housing of the gland 16 to insure againstaxial displacement of the shaft and its rotor with respect to the statorstructure. The wiper pieces 31 carried by the rotor disk are designed tobridge two adjacent contacts 17 on the stator. The present switch is adouble-pole,

double-throw switch and, consequently, two of the wiper pieces areprovided. Each wiper piece 31 may be stamped from a sheet oflow-resistance, corrosion-resistant metal such as silver or silveralloy. Wiping surfaces 32 and 33 are pressed out by an embossing tooland polished to make extended face-to-faoe contact with the polished endsurfaces of the contacts 17. Each wiper 31 is made to float on thecontacts 17 by means of an elongated hinge along one side of the wiperpiece, said hinge being substantially parallel to a median line throughthe wiping surfaces 32 and 33 of the piece.

This hinge comprises two leg portions 34 and 35, each of which terminatein hinge pins as and 37. The hinge pins are set into notches or recesses33 and 39 on the front face of the disk 33. The recesses or notches 33and 39 are conveniently and accurately made by casting raisedembossments integrally with the face of the disk as shown. When thehinge pins 35 and 37' are held in the notches 38 and 39, the respectivewiper piece 31 may pivot about the hinge but is rigidly held againstrotational displacement about the shaft. Each wiper piece 31 is formedso as to straddle the hub structure 49 of the disk and the shaft 15.

It should also be mentioned that the notches or recesses 38 and 39 areof sufiicient axial depth that the hinge pins 36 and 37 are free to moveaxially a limited distance in the notches or recesses. Consequently, thewiper surfaces 32 and 33 may be pressed against contacts 17 of differentheights. If one corner moves down, the hinge pin at the diametricallyopposite corner can move up. A pair of leaf springs 41 are providedbeneath the wipers 31 and function to maintain a pressure at a Singlepoint c'ehtrally of the wipers. The leaf springs 41 each have the samegeneral plane configuration as the wipers 31. Each spring 41 is bowedoutwardly so that a central portion thereof makes point contact with ahead 45 pressed into the wiper piece 31. Each spring 41 is formed withpins 42 and 43 of the same dimensions as the hinge pins 36 and 37 sothat the springs 41 drop into the recesses 38 and 39, respectively. Theouter corners of the bowed portion of each spring bear against the flatsurface of the disk 30 to transmit a fairly strong bias to each wiper 31through the boss 45.

The hinge pins 36 and 37 and the pins 42 and 43 are locked into thenotches 38 and 39 by a non-conducting washer 46 which may preferably beformed of nylon and which is pressed over the inner end of the shaft 15.The washer 46 is formed with two radially extending portions 50, each ofwhich has a pair of projections 51 at the distal end thereof. Theprojections 51 have inwardly facing surfaces 52 which taper toward oneanother from their proximal ends to their distal ends. The cast raisedgnbossments 55, within which the recesses 38 and 39 are formed, togetherwith the hub 40 form an embossment or boss 58, the outer periphery ofwhich is formed with outwardly facing surfaces 59 which flare outwardlyfrom the proximal end 60 of the boss to the distal end 51 thereof. Theinwardly facing surfaces 52 of the washer 46 engage the outwardly facingsurfaces 59 of the boss to retain the washer 46 in position on the bossand to thereby lock the pins 42 and 43 into the notches 38 and 39. Theembossments 55 and the hub 40 are formed with a pair of radiallyextending indentations 65, each of which receives a raised portion 66formed on the washer 46.

It has been found that the voltage breakdown path between the wipers 31is much longer in view of the fact that the charge must travel aroundthe raised portions 66 rather than directly between the legs 36 orbetween the legs 37. Also, the tapered nature of the surfaces 52 and 59makes possible a snapping on of the washer 46 which firmly locks thewasher 46 in position on the boss and the wipers 31 in assembledrelation with the raised portions 66 in the indentations 65 and betweenthe legs 36 and between the legs 37. Even so, the washer 46 can beeasily and quickly disassembled and reassembled by snapping off andsnapping on, respectively, of the washer relative to the boss 58.

It will be evident from the above description that the electrodes of therotary switch of the present invention are better insulated from oneanother than in prior art switches. It will also be evident that therotary switch of the present invention is less expensive to assemblethan certain prior art switches because the washer 46 need only besnapped on rather than cemented on. It also can be seen that there is noquestionable or doubtful securement involved in the snap on washer ofthe rotary switch of the present invention.

Whiie the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications that come within the spirit of the inventionand the scope of the claims are also desired to be protected.

The invention claimed is:

1. In a switch including an element formed of insulating material, apair of electrical contact members mounted on the element, said memberseach including a flattened metal piece having a pair of spaced legs,said element having recesses in the face thereof which recesses receivethe leg ends of the respective members, said recesses in said elementand the leg ends therein of one member being spaced from the recessesand the leg ends therein of the other member, the improvement whichcomprises a resilient washer of insulating material having projectionsat the periphery thereof which grip said element and retain said washeron said element, said element having indentations therein which extendbetween the leg ends of one member and the leg ends of the other member,and raised portions formed on said washer and extending into saidindentations.

2. The switch of claim 1 wherein said element is formed with a boss inwhich said recesses are formed, said boss having outwardly facingsurfaces which flare outwardly from the proximal end of the boss to thedistal end thereof, said washer projections being resilient and havinginwardiy facing surfaces which are tapered toward one another from theirproximal ends to their distal ends and which are complementary inconfiguration to said outwardly facing boss surfaces whereby said washersnaps onto said boss.

3. The switch of claim 2 wherein said element is a disk,

a shaft secured to said disk, said recesses being located atv pointssubstantially on a diametrical line across the disk so that said membersare fixed against rotational displacement on the disk.

4. The switch of claim 3 wherein said washer is formed of nylon; aplurality of metal contact elements with planar wiping contact surfacesdisposed in a circle in a plane perpendicular to an axial line; saidshaft being journalled on said line; said disk being coextensive with,parallel to, and spaced from said plane of the contact surfaces andkeyed to said shaft; said electrical contact members being adapted toslide across said contact surfaces; said legs of each of said pairs oflegs being in straddling relation to said shaft; said recesses and theleg ends of one of said electrical contact members being spaced in thedirection of said plane from the recesses and leg ends of the othercontact member.

No references cited.

ROBERT K. SCHAEFER, Primary Examiner.

J. R. SCOTT, Assistant Examiner.

1. IN A SWITCH INCLUDING AN ELEMENT FORMED OF INSULATING MATERIAL, APAIR OF ELECTRICAL CONTACT MEMBERS MOUNTED ON THE ELEMENT, SAID MEMBERSEACH INCLUDING A FLATTENED METAL PIECE HAVING A PAIR OF SPACED LEGS,SAID ELEMENT HAVING RECESSES IN THE FACE THEREOF WHICH RECESSES RECEIVETHE LEG ENDS OF THE RESPECTIVE MEMBERS, SAID RECESSES IN SAID ELEMENTAND THE LEG ENDS THEREIN OF ONE MEMBER BEING SPACED FROM THE RECESSESAND THE LEG ENDS THEREIN OF THE OTHER MEMBER, THE IMPROVEMENT WHICHCOMPRISES A RESILIENT WASHER OF INSULATING MATERIAL HAVING PROJECTIONSAT THE PERIPHERY THEREOF WHICH GRIP SAID ELEMENT AND RETAIN SAID WASHERON SAID ELEMENT, SAID ELEMENT HAVING INDENTATIONS THEREIN WHICH EXTENDBETWEEN THE LEG ENDS OF ONE MEMBER AND THE LEG ENDS OF THE OTHER MEMBER,AND RAISED PORTIONS FORMED ON SAID WASHER AND EXTENDING INTO SAIDINDENTATIONS.